Hi sir,
?Sir i have calculated the band structure of YVO4? and it is coming as near
about 0.5 ev .. sir as suggested by you in earlier reply that
>means band gap at gamma = 0.3058-(-8.9833)=? 8.2891
>? which is very large ??
Not necessarily, the offset of band in a periodic system is arbitrary. You?
need to know where you Fermi energy is, or which are the HOMO and LUMO of?
your system to find the gap.
I have calculated Fermi energy and it is coming as 6.108. The band gap of YVO4
is 3.9 eV experimental and DFT calculates the band gap as nearly half i..e. it
should come as 1.8 eV approx. Please help.. Thanks In advance.My Input files
are listed below...
SCF INPUT
===============================================
?&control
??? calculation='scf',
??? restart_mode='from_scratch',
??? prefix='yvo'
??? pseudo_dir = '/home/physics/pseudo/',
??? outdir='/home/physics/work/yvo/temp'
?/
?&system
??? ibrav =1, a=7.118300514, b= 7.118300514, c=6.289300454
, nat =24, ntyp= 3,? ecutwfc = 40.0,ecutrho=300,
?occupations='smearing', smearing='mp', degauss=0.01,
?/
?&electrons
??? mixing_beta = 0.7
??? diagonalization = 'david'
??? conv_thr =? 1.0e-6
/
?&ions
?/
ATOMIC_SPECIES
? Y???? 88.90585???? Y.pbe-nsp-van.UPF
? V???? 50.9415????? V.pbe-sp-van.UPF
? O???? 15.9994????? O.pbe-van_ak.UPF
ATOMIC_POSITIONS {angstrom}
Y???????????? 0.000000000?? 5.338725356??? 0.786162553
/
/
K_POINTS {automatic}
? 4 4 4 0 0 0
=======================================================
?????????????????????????????? Bands Input
======================================================
?&control
??? calculation='bands'
??? pseudo_dir = '/home/physics/pseudo/',
??? outdir='/home/physics/work/yvo/temp',
??? prefix='yvo',
?
?/
?&system
??? ibrav =1, a=7.118300514, b= 7.118300514, c=6.289300454, nat=24, ntyp=3,
ecutwfc = 40.0,ecutrho=300, occupations='smearing', smearing='mp',
degauss=0.01, nbnd= 115,
???
?/
?&electrons
?? mixing_beta=0.7
?? conv_thr=1.0e-6
?diagonalization = 'david'
/
&ions
?/
ATOMIC_SPECIES
?Y?????? 88.90585???? Y.pbe-nsp-van.UPF
? V????? 50.9415????? V.pbe-sp-van.UPF
? O???? 15.9994????? O.pbe-van_ak.UPF
ATOMIC_POSITIONS {angstrom}
Y???????????? 0.000000000?? 5.338725356??? 0.786162553
\
\
K_POINTS
?26
0.000 0.000 0.000? 1
0.000 0.000 0.125? 1
0.000 0.000 0.250? 1
0.000 0.000 0.375? 1
0.000 0.000 0.500? 1????????????????????????????
0.125 0.125 0.500? 1????????????????????????????
0.250 0.250 0.500? 1????????????????????????????
0.375 0.375 0.500? 1???????????????????????????
0.500 0.500 0.500? 1????????????????????????????
0.500 0.500 0.333? 1????????????????????????????
0.500 0.500 0.166? 1????????????????????????????
0.500 0.500 0.000? 1????????????????????????????
0.375 0.375 0.000? 1????????????????????????????
0.250 0.250 0.000? 1????????????????????????????
0.125 0.125 0.000? 1????????????????????????????
0.000 0.000 0.000? 1????????????????????????????
0.000 0.000 0.166? 1???????????????????????????
0.000 0.000 0.333? 1????????????????????????????
0.000 0.166 0.500? 1??????????????????????????
0.000 0.333 0.500? 1???????????????????????????
0.000 0.500 0.500? 1????????????????????????????
0.000 0.500 0.333? 1????????????????????????????
0.000 0.500 0.166? 1????????????????????????????
0.000 0.500 0.000? 1????????????????????????????
0.000 0.333 0.000? 1????????????????????????????
0.000 0.166 0.000? 1
============================================================
===========================================================
?&inputpp
??? prefix? = 'yvo'
??? outdir = '/home/physics/work/yvo/temp'
??? filband = 'yvobands.dat'
/
========================================
Plotband INPUTS
=======================================
yvobands.dat
-10? 12
yvobands.xmgr
yvobands.ps
6.1088
1.0? 0.00
================================================
============================================
With regards,
Neel Singh
Univeristy of Delhi
--- On Tue, 28/7/09, Lorenzo Paulatto <paulatto at sissa.it> wrote:
From: Lorenzo Paulatto <[email protected]>
Subject: Re: [Pw_forum] Not getting right Band structure
To: "PWSCF Forum" <pw_forum at pwscf.org>
Date: Tuesday, 28 July, 2009, 10:07 AM
In data 28 luglio 2009 alle ore 11:54:14, Neel Singh?
<neelphysics at yahoo.in> ha scritto:
> means band gap at gamma = 0.3058-(-8.9833)=? 8.2891
>? which is very large ??
Not necessarily, the offset of band in a periodic system is arbitrary. You?
need to know where you Fermi energy is, or which are the HOMO and LUMO of?
your system to find the gap.
> 2) In the output of SCF and Bands , the output file has 4 warnings
This a very frequently asked question, please see the corresponing entry?
in the manual:
http://www.pwscf.org/guide/2.1.2/html-node/node56.html
http://www.pwscf.org/guide/2.1.2/html-node/node57.html
> for this I have already increase the following quantities? in the???
> increments
> kinetic-energy cutoff? ???=? ? ? 40.0000? Ry to 60
>? ? ? charge density cutoff? ???=? ???250.0000? Ry to 400
> But still the warnings are there.
It is not a big increment of the cutoff that will solve this problem, but?
a small increment or nr1, nr2 nr3
cheers, and good work
--
Lorenzo Paulatto
SISSA? &? DEMOCRITOS (Trieste)
phone: +39 040 3787 511
skype: paulatz
www:???http://people.sissa.it/~paulatto/
? ???*** save italian brains ***
? http://saveitalianbrains.wordpress.com/
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